A conventional needle clamp of the type described above is disclosed in Japanese Utility Model No. 36-7062. Such a needle clamp comprises a clamp body and a clamp screw which engages with a threaded hole of the clamp body. In order to attach plural needles to a needle bar, the needles are inserted into a hole provided in the clamp body. Thereafter, the clamp screw is tightened within the threaded hole so that peripheral surfaces of the needles are wedged against an internal surface of the hole by a tapered end portion of the clamp screw.
In such a conventional needle clamp, however, it is relatively difficult to precisely machine the threaded hole for the clamp screw at a required position. If an axis of the machined threaded hole deviates from the middle position of two needles arranged side by side, the tapered portion of the clamp screw is displaced toward one needle and off of the middle position. As a result, both needles are not firmly attached to the needle bar with one clamp screw.
In order to overcome the foregoing disadvantage, an improved needle clamp has been proposed in Laid-open Japanese Publication No. 59-37986. In the proposed clamp, a spacer member is placed between a clamp screw and two needles arranged side by side. When the clamp screw is tightened, a tapered portion of the spacer member is guided along peripheral surfaces of the needles and is moved to the middle position of the needles, so that the tapered portion presses both needles simultaneously.
The needle clamp proposed in Japanese Patent No. 597986 still suffers from a substantial deficiency. The spacer member must be pivotally mounted on the needle bar so as to prevent the spacer member from falling off or from blocking the insertion of needles. Thus, construction of the needle clamp and the needle bar is complicated, rendering it difficult to machine the needle bar and to attach the needle clamp to the needle bar.